Saturday, March 5, 2011

Windows virtualization software

Previously I mentioned three bare metal hypervisor solutions -- Xen, KVM, and VMware ESXi -- and what was required to push through a video card to a WIndows VM living on those hypervisors. I have since managed to get that working with VMware ESXi, and I suspect if I install the very latest Fedora 14 host it'll work with KVM too.

That works fine with a desktop machine or rack server where I can mount multiple video cards into the box. The performance of Windows 7 virtualized is indistinguishable from Windows 7 raw. Here are my scores for Windows 7 raw on that box, with a Seagate Momentus XT 7200 RPM boot drive (due to the front-loading slot on my case that allows easy swapping of OS drives):

The problem, however, is when you want to go mobile. You simply can't add a second video card to a laptop. So if I want to play games on one of those new Dell Sandy Bridge desktop-replacement laptops, I need to run WIndows native, and come up with a way to have Linux also running and handling my years of accumulated data, all of which is in a Unix filesystem tree and cannot simply be copied into Windows. I preferably want this Linux to be running on a raw partition -- not on a file within a Windows partition -- and it has to be able to access raw Linux-formated USB and SATA drives. So, let's look at the first candidate... VMware Player

VMware Player is VMware's entry level desktop virtualization program. At one point in time VMware player would only start up virtual machines that had been created by VMware Workstation, but now it's an almost full version of VMware Workstation with various functionality like snapshots stripped out and with a limitation of only four cores allowed. VMware Player is "free" -- it's free for personal use, if you want to deploy it in a corporate environment you can license it for a fairly trivial per-seat fee (quite trivial, it'll be lost in the noise of your IT budget).

The test machine is my Xen server with Windows 7 installed as described above. I installed VMware Server on it without any problem.
I created my Scientific Linux 6.0 virtual machine with no problem, giving it 2 gigabytes of memory and a 16gb root filesystem. VMware Tools installed easily into SL6 and allowed me to treat the Linux "X" desktop as if it were just any other Windows window, I could click into it, my mouse pointer could be moved outside of the window while I was typing into Linux program, and so forth. Adding the two 2TB SATA physical hard drives to the virtual machine was as simple as point and click, though the VM had to be off to do so because VMware Player's hot-plug functionality apparently does not work with physical drives. Once I booted SL6 up, it saw the two 2TB drives and assembled the Linux software RAID arrays on it automagically, though I had to do vgchange -a -y to get SL6 to recognize the LVM volumes on the RAID arrays.

So how fast is access to those two SATA drives? On a subsequent reboot of my Linux VM, a RAID check got fired off. The two drives were being read at 105MB/sec apiece -- 210MB/sec total -- and it used less than 20% of one of my eight cores for VMware to virtualize this. My take on it is that VMware Player's fake SCSI device takes a fair chunk of CPU to virtualize, but modern multi-core CPU's are so bleepin' fast that you won't even notice (which I didn't, until I went to see).

The final thing I wanted to do was to export a NTFS-formatted volume to Windows via iSCSI. Windows 7 has Microsoft's iSCSI initiator built in. I gave both my Windows machine and my Linux VM fixed addresses (using the bridged mode for the Linux VM's virtual network card), and installed the iSCSI target daemon and utils with 'yum install scsi-target-utils'. Then I added the already existing logical volume /dev/datagroup/win7 volume to /etc/volumes/targets.conf (see that file for exact format of what you need to add) and started up the daemon with "service tgtd start". Then I went to the Windows Administrative Tools (you can get to them from the the Start Menu if you've configured them to appear there, or from the Control Panel), selected the iSCSI Initiator, told it to scan the IP address of my Linux VM, and voila, it popped up there and as a drive letter in the Windows Finder. Easy peasy! The only thing to remember is to poke a hole for iSCSI in both the Linux and Windows firewalls, or it doesn't work :). (Yes, been there, done that, heh!).

The final test was to attach a USB hard drive to the system and export it to my MacBook Pro via iSCSI and use it as a Time Machine device. When I attached the hard drive to the system, it popped up in Windows, but clicking Virtual Machine ->Removable Devices showed the new drive, and allowed me to add it to the virtual machine. I then added it to targets.conf and told the tgd daemon about it, then went to my iSCSI initiator on the MacBook (the globalSAN iSCSI initiator) and added it, then used Disk Utility to format it as a Mac volume. Then I went to Time Machine and told Time Machine to use it for backup, and... voila. It started backing up at about 20mb/sec -- or about 50% of theoretical USB2 speed, not too bad considering this is being done via WiFi, not a direct connection, and the iSCSI target is running in a virtual machine, not directly on the hardware. A copy in Windows of a 4GB file to a similar USB drive ran at 26mb/sec, and that should go faster than Time Machine writes because it's a big sequential write, not a lot of smaller files. So now I have the equivalent of one of those expensive Time Capsule thingies, except that a 2TB Western Digital drive in an external USB case costs a *lot* less! Why an external USB? Simple -- so if I ever have to restore my MacBook Pro after a disk crash (which has happened before), I can unplug it from my big server and plug it directly into the MBP for MacOS to restore the system back to pre-crash state.

So... it's clear that VMware Player will do everything I want it to do here. There's two more options to look at before calling this competition done, however: Oracle's VirtualBox, which recently released a brand new version (version 4.0.4), and Microsoft's own Windows Virtual PC, which doesn't officially support Linux but which has been made to do so. More on those later...

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About Me

I am a senior lead engineer and architect who has taken multiple products from concept to market and beyond. I am also one of the original Linux penguins -- my first Linux product hit the market in June 1996 and its latest incarnation is still running to this day.